FPC-attached optical modulator and optical transmission apparatus using same

Abstract

An optical modulator includes: an optical modulation element which is accommodated in a housing and has a signal electrode; a lead pin for inputting a high-frequency signal; a relay substrate in which a conductor pattern which electrically connects the lead pin and the signal electrode is formed; and a conductive extension portion which extends along a length direction of the lead pin in a range which includes at least a position of a connection portion between the lead pin and the conductor pattern, in which the extension portion is electrically connected to the housing.

What is claimed is: 
     
       1. An optical modulator comprising:
 an optical modulation element which is accommodated in a housing and has a signal electrode; 
 a lead pin for inputting a high-frequency signal; 
 a relay substrate in which a conductor pattern which electrically connects the lead pin and the signal electrode is formed; and 
 a conductive extension portion which extends along a length direction of the lead pin in a range which includes at least a position of a connection portion between the lead pin and the conductor pattern, 
 wherein the extension portion is electrically connected to the housing. 
 
     
     
       2. The optical modulator according to  claim 1 , wherein characteristic impedance of the connection portion in an operating frequency region of the optical modulation element before the lead pin and the conductor pattern are actually electrically connected to each other is higher than characteristic impedance of the lead pin and/or the conductor pattern. 
     
     
       3. The optical modulator according to  claim 1 , wherein a distance in which the extension portion extends in the range is larger than a thickness of the conductor pattern on the relay substrate. 
     
     
       4. The optical modulator according to  claim 1 , wherein the extension portion and a ground pattern formed on the relay substrate are electrically connected to each other by an electric conductor. 
     
     
       5. The optical modulator according to  claim 1 , wherein the extension portion is configured so as to include portions facing each other across the lead pin and enclose at least partially the lead pin in a radial direction of said lead pin by a portion which includes the portions facing each other. 
     
     
       6. The optical modulator according to  claim 5 , wherein a plurality of the lead pins are provided,
 the extension portion includes a enclosing portion which inclusively encloses at least partially at least two lead pins adjacent to each other, and 
 a distance between one of the lead pins inclusively enclosed by the enclosing portion and a lead pin which is adjacent to said one of the lead pins and is not inclusively enclosed said the enclosing portion is wider than a distance between the lead pins inclusively enclosed by said enclosing portion. 
 
     
     
       7. The optical modulator according to  claim 5 , wherein the portions facing each other are electrically connected to each other by an electric conductor disposed across an end portion in the length direction of the lead pin. 
     
     
       8. The optical modulator according to  claim 1 , wherein the extension portion is fabricated as a separate body from the housing and is fixed and electrically connected to the housing. 
     
     
       9. The optical modulator according to  claim 8 , wherein the extension portion is provided with a pedestal portion for fixing the relay substrate. 
     
     
       10. The optical modulator according to  claim 1 , wherein the extension portion is in contact with the relay substrate. 
     
     
       11. An optical transmission apparatus comprising:
 the optical modulator according to  claim 1 ; and 
 an electronic circuit which outputs an electric signal for causing the optical modulator to perform a modulation operation.